Yersinia pestis, the causative agent of plague, has high potential for use as biological weapon in the context of terrorism of warfare, and is classified as a category A agent. Its efficient person-to-person transmission via the aerosol route, the rapidly fatal course of primary pneumonic plague, the necessity for very rapid institution of antibiotic therapy, and the lack of an effective vaccine are major concerns. This project has three major goals: establishing the fundamental mechanisms that contribute to immunity against pneumonic infection with Y. pestis; determining if immunosuppressive activities that have been indirectly implicated in virulence of other yersiniae play a significant role in plague; and the discovery of small molecule inhibitors of Y. pestis virulence-enhancing functions. These inhibitors will serve as the basis for development on non-antibiotic therapeutics that may be useful in treatment of antibiotic-resistant Y. pestis, or used to extend the window in which antibiotic treatment may be efficacious. The work to be performed in this proposal will be a collaboration engaging several investigators with expertise in related areas. Specifically, we will compare the course of disease in selected mouse strains challenged by various routes including both true aerosol (collaboration with Dr. Hardy Kornfeld, UMMS) and intranasal infection to determine the most suitable models for use in subsequent experiments. These findings will be applied to studies directed towards characterizing the required elements of an immune response to Y. pestis. Additionally, we will construct and analyze genetically altered Y. pestis strains deficient in the LcrV/TLR-2 interaction thought to play an important role in immunosuppression (with Dr. Egil Lien at UMMS), devise high throughput assays and screen for low molecular weight inhibitors of type III secretion and the LcrV/TLR-2 interaction. Dr. Egil Lien at UMMS, in collaboration with Dr. Shan Lu at UMMS, will test novel antigens discovered in the immunological analysis for potential utility as vaccine components for protection against pneumonic plague. This project will heavily use proposed NERCE Cores including Proteomics, Small Molecule Screening, Biological Molecule Production, and BSL3 Animal and Tissue Culture Cores.